1. Field of the Invention
The present invention relates to a plasma display panel manufacturing apparatus, and to a manufacturing method therefor, and more particularly to an apparatus for performing integrated panel sealing, release of exhaust gas, introduction of luminescent gas or discharge gas, and vacuum sealing, and a method of manufacturing a plasma display panel using this apparatus.
2. Related Art
A plasma display panel is generally formed by a front substrate and a rear substrate which have mutually perpendicular opposing electrodes on each of the substrates, a glass tube (hereinafter referred to as an exhaust tube) mounted by low-melting-point glass so as to join a through hole provided beforehand on the rear substrate for the purpose of introducing and exhausting gas, these elements being placed in a sealing furnace so as to melt the low-melting-point glass and form the glass vessel. In addition to release of the exhaust gas via the exhaust tube, the panel is heated to release internal gas. After degassing for a prescribed amount of time in order to achieve a prescribed level of vacuum, filling is done with a gas such as neon (Ne), argon (Ar), or xenon (Xe) or a gas mixture thereof at approximately 53,200 to 79,800 Pa (400 to 600 Torr), which serves as a luminescent gas, after which a gas burner or the like is used to seal the exhaust tube thereby forming a plasma display panel with an exhaust tube.
A second known method is that of combining a rear substrate and a front substrate, and placing the combination inside a vacuum chamber, performing vacuum exhausting and degassing, and subsequent filling with a luminescent gas in the vacuum chamber, and then melting the low-melting-point glass of the peripheral part of the substrate so as to perform sealing thereof. In the case of this method, the structure is one in which there is neither an exhaust tube nor a gas introduction hole in the panel.
A third method that has been proposed is one in which a 10 to 20 mm semichip tube is provided as a gas introduction hole, this semichip tube provided on the substrate being covered by a small chamber, and residual gas within the panel being exhausted via the semichip tube, after which gas sealing is done, a halogen lamp being used to illuminate the semichip tube via a quartz window provided in the small chamber, so as to melt the semichip tube and perform sealing.
In the above-noted methods of manufacturing a plasma display panel of the prior art, however, because many minute separators having a height of 100 to 200 μm between the front substrate and the rear substrate are provided, and the conductance of the exhaust tube is small, 10 or more hours is required for vacuum exhausting degassing, making the productivity low. Additionally, there is insufficient exhausting and poor purity of the luminescent gas depending upon the lot, this manifesting itself as the problem of a tendency toward variation in the discharge characteristics.
Additionally, because the glass tube (chip tube) remaining after the exhaust tube is removed is extremely fragile, and subject to breakage with even a small shock, not only is it necessary to take extreme care when handling the panel, but also when the plasma display panel is combined with a driving electronic circuit to form a module, it is necessary to mount a protective cap, and to establish a design that avoids interference in electronic components and the printed circuit board.
With regard to the second above-noted manufacturing method of the past, in which there is no exhaust tube, although there is a significant improvement in the exhausting time, residual gas is sealed within the panel when sealing is done, thereby leading to a deterioration of the purity of the luminescent gas. Additionally, amount of costly luminescent gas used is large, causing the problem of high cost.
In the third above-noted manufacturing method of the past, although the problem of the second method is solved, a protruding exhaust tube remains on the panel, thereby requiring the same type of care in handling as with a conventional panel with an exhaust tube.
In Japanese Utility Model (KOKOKU) No. 5-48354, a display apparatus for PDP panel in which a gas inlet hole is sealed by a cover member, is disclosed.
In Japanese Utility Model (KOKOKU) No. 6-9437, a jig for fabricating a display apparatus for PDP panel, is disclosed. In this invention, a mechanism for the purpose of sealing a gas inlet hole is described.
In IDW'97 meeting, “Vacuum process for plasma display panel without exhaust pipe” is reported by Y. Shimamoto et al. This newly developed process is composed of vacuum exhausting, luminescent gas filling and frit sealing steps. However, these inventions do not solve above mentioned drawbacks.
Accordingly, in order to improve on the above-noted drawbacks associated with the prior art, it is an object of the present invention to provide a novel apparatus and a method for manufacturing a plasma display panel, whereby degassing is completed in a short amount of time, with a small amount of residual gas, this being achieved without an exhaust tube.